diff -ur mutt-1.9.0.orig/init.h mutt-1.9.0/init.h
--- mutt-1.9.0.orig/init.h	2017-09-04 16:48:21.409528002 +0200
+++ mutt-1.9.0/init.h	2017-09-04 16:49:26.505093636 +0200
@@ -3510,7 +3510,7 @@
   */
 #  endif /* defined HAVE_SSL_PARTIAL_CHAIN */
 # endif /* defined USE_SSL_OPENSSL */
-  { "ssl_ciphers", DT_STR, R_NONE, {.p=&SslCiphers}, {.p=0} },
+  { "ssl_ciphers", DT_STR, R_NONE, {.p=&SslCiphers}, {.p="@SYSTEM"} },
   /*
   ** .pp
   ** Contains a colon-separated list of ciphers to use when using SSL.
diff -ur mutt-1.9.0.orig/mutt_ssl_gnutls.c mutt-1.9.0/mutt_ssl_gnutls.c
--- mutt-1.9.0.orig/mutt_ssl_gnutls.c	2017-09-04 16:48:21.403528134 +0200
+++ mutt-1.9.0/mutt_ssl_gnutls.c	2017-09-04 16:51:16.081679141 +0200
@@ -286,6 +286,8 @@
   else
     mutt_buffer_strcpy (priority, "NORMAL");
 
+if (SslCiphers && strcmp(SslCiphers, "@SYSTEM"))
+{
   if (!option (OPTTLSV1_3))
   {
     nproto--;
@@ -313,6 +315,7 @@
     mutt_error (_("All available protocols for TLS/SSL connection disabled"));
     goto cleanup;
   }
+}
 
   if ((err = gnutls_priority_set_direct (data->state, mutt_b2s (priority), NULL)) < 0)
   {